Electronic flash, electronic camera and light emitting head

ABSTRACT

The present invention is directed to a light emitting head for use with an electronic camera. The light emitting head is preferably formed as an array of red, green, and blue light emitting diodes (LEDs) provided on the sides of a light guide member, preferably a polygonal prism. A reflecting mirror is arranged on the bottom of the prism, and reflecting elements are provided on the sides of the prism that are not in contact with the LEDs such that, in operation, light from the LEDs is emitted through the top of the prism and prevented from leaking through the sides. A diffusion plate is provided on the emission surface, and the number of green LEDs is larger than the number of red and blue LEDs to produce a white light. In other embodiments, the light guide member is a cylinder or formed entirely as a diffusion plate.

This application is a Divisional of application Ser. No. 09/911,736,filed on Jul. 5, 2001 now U.S. Pat. No. 7,106,378, and for whichpriority is claimed under 35 U.S.C. § 120; and this application claimspriority of Application No. 2000-223505 filed in Japan on Jul. 25, 2000and Application No. 2001-210598 filed in Japan on Jul. 11, 2001 under 35U.S.C. § 119; the entire contents of all are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an electronic flash, anelectronic camera, and a light emitting head. The present inventionrelates more particularly to an electronic flash using light-emittingdevices such as light emitting diodes (LEDs), an electronic camera and alight emitting head.

2. Description of the Related Art

An electronic flash of a camera has a xenon tube as a light source.

There have been high-luminance LEDs that emit red, green, amber, yellow,and milky-white lights, and a high-luminance blue LEDs has been used.These LEDs are mainly used as indicators of various apparatuses.

However, when an electronic flash is used to perform back lightcorrection for the sun light in the morning or evening, the colors ofthe picture can be unnatural since the spectral characteristics of thexenon tube are close to those of the daylight. Also, the electronicflash with the xenon tube can emit the light for only a fewmilliseconds, and it can not be used for slow shutter speeds.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a new electronic flash of a camera using LEDs.

It is an object of the present invention to provide an electronic flashof a camera and an electronic camera that manually or automaticallychanges a color temperature of an electronic flash light to preventunnatural colors of a picture.

It is an object of the present invention to provide a light emittinghead that can be applied to an electronic flash with light emittingdevices such as LEDs.

To achieve the above-mentioned object, the present invention is directedto an electronic flash of a camera, comprising: an electronic flashlight source comprising a light emitting diode; and a light emissioncontrol device that makes the electronic flash light source emit lightby supplying electric energy to the light emitting diode.

The electronic flash light source preferably comprises R, G and B lightemitting diodes.

Preferably, the electronic flash further comprises a color temperaturesetting device that manually sets a color temperature of the lightemitted from the electronic flash light source, wherein the lightemission control device controls ratios between light emission amountsof the R, G and B light emitting diodes so that a color temperature ofthe light emitted from the electronic flash light source becomes thecolor temperature set by the color temperature setting device.

Preferably, the electronic flash further comprises a color temperaturedetermining device that determines a color temperature of subject light,wherein the light emission control device controls ratios between lightemission amounts of the R, G and B light emitting diodes so that a colortemperature of the light emitted from the electronic flash light sourcebecomes the color temperature determined by the color temperaturedetermining device. Thus, the color temperature of the electronic flashlight can be automatically controlled to that of the subject light, andthis can prevent unnatural colors of the picture.

Preferably, the electronic flash further comprises a capacitor with alarge capacity that is charged by a battery, wherein the light emissioncontrol device supplies the electric energy from the capacitor to thelight emitting diode. Thus, the electric energy can be obtained with thesmall battery. In addition, fall of the voltage of the battery can beprevented at the light emission, and misoperation of the other circuitscan be prevented.

Preferably, the electronic flash further comprises a temperature sensorthat determines a peripheral temperature of the light emitting diode,wherein the light emission control device controls the electric energyto obtain a desired light emission amount according to the peripheraltemperature determined by the temperature sensor. Though the lightemitting diodes change the light emitting amounts due to theirperipheral temperature, the desired light emission amount can still beobtained.

To achieve the above-mentioned object, the present invention is directedto an electronic flash of a camera, comprising: an electronic flashlight source that emits electronic flash light; and an adjusting devicethat adjust a color temperature of the electronic flash light emittedfrom the electronic flash light source.

Preferably, the adjusting device comprises a color temperature settingdevice that manually sets a color temperature of the electronic flashlight; and a light emission control device that controls a colortemperature of the electronic flash light to the color temperature setby the color temperature setting device.

Preferably, the adjusting device comprises a color temperaturedetermining device that determines a color temperature of subject light;and a light emission control device that controls a color temperature ofthe electronic flash light to the color temperature determined by thecolor temperature determining device.

Preferably, the color temperature determining device has determiningdevices that convert color components of the subject light into electricsignals and determines the color temperature of the subject lightaccording to a ratio between determination signals of the determiningdevices. The determining devices may be red and blue determining devicesor red, green and blue determining devices.

The color temperature determining device can determine the colortemperature of the light source according to color image signals of asubject image captured by imaging devices of the camera. The imagingdevices of the camera can be also used as a part of the colortemperature determining device.

Preferably, the electronic flash light source is R, G and B lightemitting devices and light emitting amounts from the R, G and B lightemitting devices can be separately controlled. The R, G and B lightemitting devices can be light emitting diodes, organicelectroluminescences or plasma light emitting devices.

Preferably, the electronic flash further comprises a capacitor with alarge capacity that is charged by a battery, and the adjusting devicesupplies the electric energy from the capacitor to the light emittingdevices.

Preferably, the electronic flash further comprises a temperature sensorthat determines a peripheral temperature of the light emitting diodes,and the adjusting device controls the electric energy to obtain adesired light emission amount according to the peripheral temperaturedetermined by the temperature sensor.

Preferably, the adjusting device adjusts the color temperature of theelectronic flash light by controlling a ratio between the light emittingamounts from the R, G and B light emitting devices.

The adjusting device can control the ratio between the light emittingamounts from the R, G and B light emitting devices by separately turningon and off the R, G and B light emitting devices.

Preferably, the adjusting device comprises a light adjusting sensor thatdetermines one of an amount of reflected light from a subject emittedfrom one of the R, G and B light emitting devices of which lightemitting amount is smallest among the R, G and B light emitting devicesand an amount of reflected light from the subject emitted from the R, Gand B light emitting devices; a first light emission controlling devicethat stops light emission of the one of the R, G and B light emittingdevices when the one of the amounts determined by the light adjustingsensor reaches a predetermined reference value according to the ratiosbetween the light emitting amounts from the R, G and B light emittingdevices; a measuring device that measures a light emitting time of theone of the R, G and B light emitting devices; a calculating device thatcalculates light emitting times of others of the R, G and B lightemitting devices according to the light emitting time measured by themeasuring device and the ratios between the light emitting amounts fromthe R, G and B light emitting devices; and a second light emissioncontrolling device that stops light emission of the others of the R, Gand B light emitting devices according to the light emitting timescalculated by the calculating device. The light emitting amount (lightemitting time) of the light emitting devices with the smallest lightemitting amount is controlled according to the amount determined by thelight adjusting sensor. The light emitting times of the other lightemitting devices are calculated according to the light emitting time andthe ratio between the light emitting amounts from the R, G and B lightemitting devices.

Preferably, the adjusting device comprises a device that turns on andoff the R, G and B light emitting devices with duty ratios correspondingto the ratios between the light emitting amounts from the R, G and Blight emitting devices; a light adjusting sensor that determines anamount of reflected light from a subject emitted from the R, G and Blight emitting devices; and a light emission controlling device thatstops light emission of the R, G and B light emitting devices when theamount determined by the light adjusting sensor reaches a predeterminedreference value.

The adjusting device may comprise a device that turns on and off R, Gand B light emitting devices of numbers according to the ratios betweenthe light emitting amounts from the R, G and B light emitting devices; alight adjusting sensor that determines an amount of reflected light froma subject emitted from the R, G and B light emitting devices; and alight emission controlling device that stops light emission of the R, Gand B light emitting devices when the amount determined by the lightadjusting sensor reaches a predetermined reference value.

Preferably, the electronic flash light source comprises: a white lightsource that emits white electronic flash light; and color filters thatare arranged movably in front of the white light source, wherein theadjusting device adjusts the color temperature of the electronic flashlight by moving at least one of the color filters in front of the whitelight source.

To achieve the above-mentioned object, the present invention is directedto an electronic camera that stores color image signals of a subjectimage captured with a taking lens and an imaging device, the electroniccamera comprising: a color temperature determining device thatdetermines a color temperature of subject light before a shooting; anelectronic flash light source that emits electronic flash light; anautomatic white balance correcting device that corrects a white balanceof the color image signals according to the color temperature determinedby the color temperature determining device at the shooting irrespectiveof light emission of the electronic flash light source; and an adjustingdevice that adjusts a color temperature of the electronic flash light tothe color temperature determined by the color temperature determiningdevice.

The electronic camera emits the light with the color temperature that isthe same as the color temperature of the subject light source, and thewhite balance is corrected according to the color temperature of thesubject light source. The conventional electronic camera corrects thewhite balance no matter what the color temperature of the subject lightsource is.

To achieve the above-mentioned object, the present invention is directedto an electronic camera that stores color image signals of a subjectimage captured with a taking lens and an imaging device, the electroniccamera comprising: a color temperature determining device thatdetermines a color temperature of subject light; a recording device thatrecords at least one color temperature determined by the colortemperature determining device; a designating device that reads thecolor temperature recorded in the recording device; an automatic whitebalance correcting device that corrects a white balance of the colorimage signals according to the color temperature read by the designatingdevice; an electronic flash light source that emits electronic flashlight; and an adjusting device that adjusts a color temperature of theelectronic flash light to the color temperature read by the designatingdevice. For example, the user records color temperatures of a spotlightof a ceremonial hall, a ceiling light and a studio light, and reads oneof the color temperatures so that the electronic flash emits the lightwith the read color temperature, and the white balance is correctedaccording to the color temperature.

The color temperature determining device can determine the colortemperature of the subject light from the color image signals of thesubject image captured with the taking lens and the imaging device.

To achieve the above-mentioned object, the present invention is directedto a an optical member that is one of a polygonal prism and a cylinder;a light emitting device array provided on a side of the optical member;and a reflecting mirror provided on at least a bottom of the opticalmember, wherein the light emitting device array emits light out of theoptical member through a top of the optical member.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature of this invention, as well as other objects and advantagesthereof, will be explained in the following with reference to theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures and wherein:

FIG. 1 is a perspective view of an electronic flash of a camera of afirst embodiment according to the present invention;

FIG. 2 is a back view of the electronic flash in FIG. 1;

FIGS. 3(A) and 3(B) are views showing a light source part of alight-emitting part in FIG. 1;

FIG. 4 is a block diagram of the electronic flash in FIG. 1;

FIGS. 5(A), 5(B), 5(C), 5(D), 5(E), 5(F) and 5(G) are timing chartsshowing an operation of a system controller in FIG. 3;

FIG. 6 is a circuit diagram showing another method of controlling lightemitting amounts of LEDs;

FIG. 7 is a timing chart showing a color temperature controlling methodin which light emitting times of the LEDs are separately controlled;

FIG. 8 is a timing chart showing a color temperature controlling methodin which a duty ratio of the LEDs is controlled;

FIG. 9 is a block diagram showing a second embodiment of an electronicflash of the camera according to the present invention;

FIG. 10 is a block diagram showing a third embodiment of an electronicflash of the camera according to the present invention;

FIG. 11 is a block diagram showing a fourth embodiment of an electronicflash of the camera according to the present invention;

FIG. 12 is a back view of an electronic camera that can adjust a colortemperature of an electronic flash light according to the presentinvention;

FIG. 13 is a block diagram showing an inner structure of the electroniccamera in FIG. 12;

FIG. 14 is a block diagram of an electronic flash that is built in orattached to the electronic camera in FIG. 12; and

FIG. 15 is a perspective view of a diode light emitting head accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention will be described in further detail by way of examplewith reference to the accompanying drawings.

FIG. 1 is a perspective view of an electronic flash 10 for a camera of afirst embodiment according to the present invention.

The electronic flash 10 is composed of a body 20 with a hot shoe 22 onits bottom and a light-emitting part 30.

Color temperature sensors 24 (photo sensors 24R, 24G and 24B with R, Gand B filters) for measuring a color temperature of subject light areprovided on the front of the body 20. A switch 26 for choosing a manualmode or an automatic mode and a color temperature setting switch 28 areprovided on the side of the body 20. In the manual mode, a user manuallysets a color temperature of an electronic flash light with a colortemperature setting switch 28. In the automatic mode, the colortemperature of the electronic flash light is automatically set.

A reference numeral 32 denotes a Fresnel lens of the light-emitting part30, and a reference numeral 34 denotes a light-receiving sensor foradjusting the electronic flash light.

FIG. 2 is a back view of the electronic flash 10. Color temperaturerecording switches 21 (21-1, 21-2 and 21-3), indicators L1, L2 and L3and a color temperature reading switch 23 are provided on the back ofthe electronic flash 10. When one of the color temperature recordingswitches 21 is pressed, the current color temperature of the subjectlight measured by the color temperature sensors 24 is recorded in anonvolatile memory (EEPROM) 25 (see FIG. 4) of the electronic flash 10.The three color temperature recording switches 21 make it possible torecord three color temperatures.

Each time the color temperature reading switch 23 is pushed, one of thecolor temperatures recorded with the color temperature recordingswitches 21-1, 21-2 and 21-3 is read in order. The indicators L1, L2 andL3 correspond to the color temperature recording switches 21-1, 21-2 and21-3, respectively, and one of the indicators L1, L2 and L3corresponding to the selected color temperature is turned on. The colortemperature of the electronic flash light is adjusted to the read colortemperature.

FIG. 3(A) is a section of a light source part 36 of the light-emittingpart 30, and FIG. 3(B) is a front view of the light source part 36.

The light source part 36 is composed of a reflector 37, LEDs 38 (R, Gand B LEDs 38R, 38G and 38B) and a diffusion plate 39. The R, G and BLEDs 38R, 38G and 38B are arranged to form an array as shown in FIG.3(B). The diffusion plate 39 diffuses high-directivity lights emittedfrom the LEDs 38. The numbers of the LEDs 38R, 38G and 38B does not needto be the same, and they are preferably arranged so that a white lightis produced when all the LEDs 38 emit lights.

FIG. 4 is a block diagram of the electronic flash 10.

The electronic flash 10 has a battery 40, a step-up transformer 42, alarge-capacity capacitor 44, operational amplifiers 46, 48 and 50, asystem controller 52, a light adjusting circuit 54 and a temperaturesensor 56 as well as the color temperature recording switches 21, thecolor temperature reading switch 23, the color temperature sensors 24,the EEPROM 25, the switch 26, the color temperature setting switch 28,the light-receiving sensor 34 and the LEDs 38.

The system controller 52 controls the electronic flash 10, and makes thestep-up transformer 42 output the voltage of 10V from the voltage (forexample, 6V) of the battery 40 in order to charge the capacitor 44 withthe outputted voltage. The capacitor 44 is charged for two to fiveseconds, and can discharge to the LEDs 38 for more than 1/60 sec(approximately 16 ms).

The capacitor 44 discharges to the LEDs 38R, 38G and 38B through theoperational amplifiers 46, 48 and 50, and the system controller 52controls the operational amplifiers 46, 48 and 50 to control alight-emitting time and amount of the LEDs 38R, 38G and 38B.

The system controller 52 receives a light-emitting signal from thecamera through the hot shoe 22 (see FIG. 1) in synchronization with ashutter release, and receives information (a guide number, etc.) fordetermining the light-emitting amount in a serial communication. Whenthe switch 26 is on the manual mode, the system controller 52 controlsthe color temperature of the electronic flash light to that set with thecolor temperature setting switch 28. When the switch 26 is on theautomatic mode, the system controller 52 controls the color temperatureof the electronic flash light to that of the subject light determined bythe color temperature sensors 24. The color temperature sensors 24 arenot limited to those. They determine the color temperature of thesubject light according to the ratio between the R, G and B componentsof the light, but they may do that according to the ratio between the Rand B components of the light.

When one of the color temperature recording switches 21 is pushed, thesystem controller 52 records the current color temperature of thesubject light determined by the color temperature sensors 24 in theEEPROM 25. When one of the color temperature reading switches 23 ispushed, the system controller 52 reads the recorded color temperature,and controls the color temperature of the electronic flash light to theread color temperature. For example, the user records color temperaturesof a spotlight of a ceremonial hall, a ceiling light and a studio lightwith the color temperature sensors 24 in the EEPROM 25, and reads one ofthe color temperatures with one of the color temperature readingswitches 23 so that the electronic flash emits the light with the readcolor temperature.

Since the light amounts of the LEDs change according to their peripheraltemperature, a temperature sensor 56 that determines the peripheraltemperature of the LEDs 38 is provided. The system controller 52controls the electric current to the LEDs 38 according to the peripheraltemperature determined by the temperature sensor 56.

The operation of the system controller 52 will now be explained withreference to timing charts of FIGS. 5(A), 5(B), 5(C), 5(D), 5(E), 5(F)and 5(G).

On receiving an electronic flash signal (FIG. 5(A)), the systemcontroller 52 outputs a signal to the step-up transformer 42 forstarting the charging of the capacitor 44. When the charging isfinished, the system controller 52 stops the step-up transformer 42(FIGS. 5(B) and 5(C)).

When a shutter release button is half pressed, the system controller 52gets ready for the discharging (FIG. 5(D)) and receives the information(the guide number, etc.) for determining the light emitting amount. Whenthe switch 26 is on the automatic mode, the system controller 52 readsthe color temperature of the subject light from one of the colortemperature sensors 24. When the switch 26 is on the manual mode, thesystem controller 52 reads the manually-set color temperaturecorresponding to the operated color temperature reading switch 23 (FIG.5(E)).

The system controller 52 determines the light emitting amount accordingto the received information, outputs a reference value for the lightemitting amount to the light adjusting circuit 54, determines the ratiobetween the light emitting amounts of the LEDs 38R, 38G and 38Baccording to the color temperature of the subject light, and sets R, Gand B light emitting levels from the ratio (FIG. 5(F)).

When the shutter release button is fully pressed, the system controller52 receives the light emitting signal in synchronization with theshutter release and outputs the R, G and B light emitting levels topositive-sequence input terminals of the operational amplifiers 46, 48and 50. Signals that corresponds to electric currents to be sent to theLEDs 38R, 38G and 38B are inputted to negative-sequence input terminalsof the operational amplifiers 46, 48 and 50, and the operationalamplifiers 46, 48 and 50 control the electric currents flowing throughthe LEDs 38R, 38G and 38B according to the R, G and B light emittinglevels.

The LEDs 38 emit the lights with the same color temperature as that ofthe subject light (FIG. 5(G)).

The light adjusting circuit 54 determines the light emitting amount withthe light-receiving sensor 34. When the light emitting amount reachesthe reference value, the light adjusting circuit 54 outputs thelight-emission stop signal to the system controller 52, which outputs asignal for stopping the light emission of the LEDs 38 to the operationalamplifiers 46, 48 and 50. This turns off the electric currents flowingthrough the LEDs 38 to stop the light emission of the LEDs 38.

FIG. 6 is a circuit diagram showing another method of controlling thelight emitting amounts of the LEDs 38.

The electric currents flow from the capacitor 44 to the LEDs 38 throughtransistors 61, 62 and 63 and inductors 64, 65 and 66.

A step-down transformer 60 receives signals indicating R, G and Blight-emitting levels, the light-emission signal in synchronization withthe shutter release, and the light-emission stop signal. After receivingthe light-emission signal, the step-down transformer 60 outputs pulseswith a controlled duty ratio to bases of the transistors 61, 62 and 63so that the electric currents corresponding to the light-emitting levelsflow through the LEDs 38 until receiving the light-emission stop signal.

The transistors 61, 62 and 63 turn on and off due to the pulses, andpass the electric currents to the LEDs 38R, 38G and 38B through theinductors 64, 65 and 66 while they are on. While they are off, electriccurrents flows to the LEDs 38R, 38G and 38B through diodes 67, 68 and 69due to induction electromotive forces of the inductors 64, 65 and 66.

The step-down transformer 60 monitors the electric currents flowingthrough the LEDs 38, and adjusts the duty ratio of the pulses inputtedto the transistors 61, 62 and 63 according to the light emitting levels.

As shown in FIG. 7, light-emitting times of the LEDs 38R, 38G and 38Bmay be controlled for a desired ratio between the light-emitting amountsof the LEDs 38.

When the ratio between the B, R and G light-emitting amounts (the sameas the ratio between the light-emitting times, for convenience) is1:2:4, the LEDs 38R, 38G and 38B start emitting the lights at one time,and the LEDs 38B stop emitting the lights a time t later, and the LEDs38R stop emitting the lights a time 2 t later, and the LEDs 38G stopemitting the lights a time 4 t later.

The time t will be explained.

A reference value V_(ref)′ is calculated by the following equation 1,V _(ref)′={3a/(a+b+c)}×V _(ref)  equation 1,

-   -   wherein V_(ref) is the reference value for adjusting the        light-emission amounts and a:b:c (a≦b≦c) is the ratio between        the light-emitting amounts.

When the ratio a:b:c is 1:2:4 as shown in FIG. 7, the reference valueV_(ref)′ is ( 3/7) V_(ref).

The LEDs 38R, 38G and 38B start emitting the lights at one time, and thelight adjusting circuit 54 determines the light emission amount with thelight-receiving sensor 34. When the light emission amount reaches thereference value V_(ref)′, the LEDs with the lowest light emission amount(the LEDs 38B in this case) stop emitting the lights, and the lightemission time t is measured. Then, the light emission times of the otherLEDs according to the light emission time t and the ratio (a:b:c) arecalculated. In case of the ratio 1:2:4, the light emission time of theLEDs 38R is 2 t, and the light emission time of the LEDs 38G is 4 t. Inthe embodiment, the light-receiving sensor 34 that is sensitive to allthe R, G and B lights, but a light-receiving sensor that is sensitiveonly to the lights with the lowest light emission amount may be used. Inthis case, the number 3 a in the equation 1 is replaced with the numbera.

FIG. 8 shows a case in which the duty ratios of the LEDs 38R, 38G and38B are adjusted to control the color temperature of the electronicflash light (the ratio between the R, G and B light-emission amounts).

The duty ratios of the LEDs 38R, 38G and 38B are determined so that theratio between the total light-emitting times of the LEDs 38 is the ratiobetween the R, G and B light emission amounts.

The LEDs 38R, 38G and 38B start emitting the lights at one time, and endit at one time when the light emission amount reaches the desiredamount.

If each LED can be turned on and off, the numbers of the LEDs 38R, 38Gand 38B to be turned on may be controlled.

FIG. 9 is a block diagram showing a second embodiment of an electronicflash 70 of the camera according to the present invention.

Unlike the electronic flash 10 of the first embodiment, the electronicflash 70 does not adjust the color temperature and has only amilky-white LED 71. Switches S1 and S2 turn on and off with anelectronic flash switch. When the switches S1 and S2 are turned on, astep-up transformer 73 outputs a voltage from that of a battery 72 tocharge a capacitor 74. When the switch S1 is turned on, an LED 75 forindicating the charging is turned on. When the voltage of the capacitor74 reaches a reference voltage inputted to an operational amplifier 76,the charging is finished and the LED 75 turns off.

A switch S3 is a normally open switch, and it is closed for an instantwhen the shutter release button is pushed.

When the switch S3 is open, a capacitor 78 is charged to more than apredetermined voltage with a light-receiving sensor 77 for the lightadjusting, and an operational amplifier 79 outputs an L-level signal toturn off a transistor 80. Thus, the electric current does not flowthrough the LED 71 and it does not emit a light even when the capacitor74 for the light emission has been charged.

When the shutter release button is pushed and the switch S3 is closed,the capacitor 78 discharges and the operational amplifier 79 outputs anH-level signal to turn on the transistor 80. This allows the flow ofelectric current from the capacitor 74 to the LED71, which emits thelight.

Then, the capacitor 78 is charged with the light-receiving sensor 77 forthe light adjusting. When the voltage of the capacitor 78 reaches thatof a resistor 81, the operational amplifier 79 outputs the L-levelsignal to turn off the transistor 80. This turns off the LED71.

A resistance of an adjustable resistor 82 can be adjusted according tothe guide number, and this changes the voltage of the resistor 81 toadjust the light emission amount of the LED 71. A switch S4 that turnson with the shutter release button may be provided instead of anautomatic electronic flash circuit (including the light-receiving sensor77 for the light adjusting) which is enclosed by a dashed line.

FIG. 10 is a block diagram showing a third embodiment of an electronicflash 90 of the camera according to the present invention.

Unlike the electronic flash 10 of the first embodiment, the electronicflash 90 has an organic electroluminescence panel (organic EL panel) 91.Parts that are the same as those in FIG. 4 are denoted by the samereference numerals, and they will not be explained in detail.

The organic EL panel 91 is formed in such a manner that R organic ELswhose spectrum peak wavelength is 600-740 nm (red area), G organic ELswhose spectrum peak wavelength is 500-600 nm (green area) and B organicELs whose spectrum peak wavelength is 380-500 nm (blue area) arearranged in the same way as the LEDs 38 in FIG. 3(B). Light emittingbrightnesses and times of the R, G and B organic ELs are controlledaccording to control signals inputted from the system controller 52.

This enables the organic EL panel 91 to emit a light with the desiredcolor temperature.

A plasma light-emitting device panel in which plasma light-emittingdevices are arranged as an array may be used instead of the organic ELpanel 91. The plasma light-emitting devices stimulates R, G and Bfluorescent materials by emitting ultraviolet rays to make them emit R,G and B lights.

FIG. 11 is a block diagram showing a fourth embodiment of an electronicflash 92 of the camera according to the present invention.

Unlike the electronic flash 10 of the first embodiment, the electronicflash 92 has a light source that can change the color temperature of theelectronic flash light with color filters 94. Parts that are the same asthose in FIG. 4 are denoted by the same reference numerals, and theywill not be explained in detail.

The light source is composed of a light emitting part 93 that emits awhite light, the color filters 94 (an R filter 94R and a B filter 94B)and a filter driving motor 95.

The color filters 94 are movably provided in front of the light emittingpart 93, and a rack 94A is connected to one end of the color filters 94.A pinion 95A engaged with the rack 94A is fixed to a driving shaft ofthe filter driving motor 95. Driving the filter driving motor 95 movesthe color filters 94 vertically in FIG. 11.

The light source emits a light with the color temperature (5500-6000degrees Kelvin) of the daytime sun when the light emitting part 93 isnot covered as shown in FIG. 11. When the R filter 94R covers the lightemitting part 93, the light source emits a light with the colortemperature (2000-3000 degrees Kelvin) of the rising or setting sun.When the B filter 94B covers the light emitting part 93, the lightsource emits a light with the color temperature (10000-20000 degreesKelvin) of the blue sky.

When the color temperature of the electronic flash light is setautomatically or manually, the system controller 52 controls the filterdriving motor 95 to move the color filters 94 for the light with thecolor temperature that is the closest to the set color temperature. Whenthe shutter release button is fully pushed and the system controller 52receives the light emission signal in synchronization with the shutterrelease, the system controller 52 outputs an electronic flash ON signalto the light emitting part 93 to emit the light.

The light adjusting circuit 54 determines the light emission amount withthe light-receiving sensor 34 for the light adjusting. When the lightemission amount reaches a reference value, the light adjusting circuit54 outputs an electronic flash OFF signal to the light emitting part 93to stop the light emission.

FIG. 12 is a back view of an electronic camera 100 that can adjust thecolor temperature of the electronic flash light according to the presentinvention.

The user rotates a mode dial 101 to set one of shooting modes includinga manual shooting mode, an automatic shooting mode and a person shootingmode. A shutter release button 102 is provided in the center of the modedial 101, and the shutter release button 2 can be pushed half and fully.

As shown in FIG. 12, an eyepiece 103, a shift key 104, a display key105, a record mode/play mode switch 106, a cancel key 107, an executionkey 108, a multifunction cross key 109 and a liquid crystal monitor 152are provided on the back of the digital camera.

FIG. 13 is a block diagram showing the inner structure of the electroniccamera 100 in FIG. 12.

A subject image formed on a light-receiving surface of a charge coupleddevice (CCD) 114 through a taking lens 110 and a diaphragm 112 isconverted into signal electric charges corresponding to the amount of anincident light by each sensor. The stored signal electric charges areread out to shift registers with read gate pulses applied from a CCDdriving circuit 116, and sequentially read out as voltage signalscorresponding to the signal electric charges with register transferpulses. The CCD 114 has an electric shutter function for controlling theexposure time (shutter speed) by outputting the stored signal electriccharges with shutter gate pulses.

The voltage signals are outputted from the CCD 114 to a correlativedouble sampling circuit (CDS circuit) 118, which samples and holds R, Gand B signals of each pixel. The CDS circuit 118 outputs the R, G and Bsignals to an A/D converter 120, which converts the R, G and B signalsinto digital R, G and B signals and outputs the digital R, G and Bsignals. The CCD driving circuit 116, the CDS circuit 118 and the A/Dconverter 120 are synchronized by timing signals outputted from a timinggenerator 122.

The digital R, G and B signals outputted from the A/D converter 120 aretemporarily stored in a memory 124, and then outputted to a digitalsignal processing circuit 126. The digital signal processing circuit 126comprises a synchronizing circuit 128, a white balance adjusting circuit130, a gamma correcting circuit 132, a YC signal producing circuit 134and a memory 136.

The synchronizing circuit 128 converts the dot-sequential R, G and Bsignals read from the memory 124 into synchronous R, G and B signals,which are outputted to the white balance adjusting circuit 130. Thewhite balance adjusting circuit 130 has multipliers 130R, 130G and 130Bthat increases or decreases digital values of the R, G and B signals,and the R, G and B signals are inputted to the multipliers 130R, 130Gand 130B, respectively. White balance correction values (gains) Rg, Ggand Bg for adjusting the white balance are outputted from a centralprocessing unit (CPU) 138 to the multipliers 130R, 130G and 130B,respectively. Each of the multipliers 130R, 130G and 130B multiplies thecorresponding digital value and gain together, and the multipliers 130R,130G and 130B get R′, G′ and B′ signals. The white balance adjustingcircuit 130 outputs the R′, G′ and B′ signals to the gamma correctingcircuit 132. The gains Rg, Gg and Bg will be later explained in detail.

The gamma correcting circuit 32 corrects the R′, G′ and B′ signals to R,G and B signals with desired gamma characteristic and outputs the R, Gand B signals to the YC signal producing circuit 134. The YC signalproducing circuit 134 produces luminance signals Y and chroma signals Crand Cb (YC signals) from the R, G and B signals. The YC signals arestored in the memory 136.

The YC signals are read from the memory 136 and outputted from theliquid crystal monitor 152 so that a moving image or a still image isdisplayed on the liquid crystal monitor 152.

After the shooting, the YC signals are compressed with a predeterminedformat by the compressing/decompressing circuit 154, and the compressedimage data is stored in a storage medium such as a memory card by astorage part 156. In the reproducing mode, the image data stored in thememory card or the like is decompressed, and the decompressed image datais outputted to the liquid crystal monitor 152 so that the image isdisplayed on the liquid crystal monitor 152.

The CPU 138 controls the circuits according to inputs from a cameracontrol part 140 including the mode dial 101, the shutter release button102 and the cross key 109. The CPU 138 also controls automatic focusing,automatic exposure and automatic white balance. For example, theautomatic focusing is contrast automatic focusing that moves the takinglens 110 through a driving part 142 so that the high-frequency componentof the G signal is the maximum when the shutter release button 102 ishalf pressed.

In the automatic exposure, the R, G and B signals are read, and thesubject brightness (exposure values) is determined according tointegrated values of the R, G and B signals. The F-number and theshutter speed are determined from the exposure value. When the shutterrelease button 102 is fully pressed, the CPU 138 drives the diaphragm112 through a diaphragm driving part 144 for the determined F-number,and controls the exposure time for the determined shutter speed. Imagedata of one frame is captured and processed, and then stored in thestorage medium.

The method of correcting the white balance will now be explained.

To manually correct the white balance, the user chooses the record modewith the record mode/play mode switch 106 and selects the manualshooting mode with the mode dial 101. Then, the user pushes theexecution key 108 to display a menu for setting the white balance on theliquid crystal monitor 152 as shown in FIG. 12, and selects an icon(AUTO, icons showing subject light sources, and M) with the cross key109. When the icon “AUTO” is selected, the color temperature of thesubject light (the type of the subject light source) is measured and thewhite balance is corrected according to the color temperature. When oneof the icons showing the light sources is selected, the white balance iscorrected according to the subject light source. When the icon “M” isselected, a recorded color temperature is read and the white balance iscorrected according to the color temperature.

The measurement of the color temperature of the subject light (the typeof the subject light source) in the automatic shooting mode or when theicon “AUTO” is selected in the manual shooting mode will be explained.

The image is divided into multiple areas (8 by 8), and an integratingcircuit 148 in FIG. 13 calculates average values of the R, G and Bsignals in each area stored in the memory 124 and outputs them to theCPU 138. Multipliers 150R, 150G and 150B are provided between theintegrating circuit 148 and the CPU 138, and gains are inputted to themultipliers 150R, 150G and 150B.

The CPU 138 determines the subject light source (daylight,shade-cloudiness, a fluorescent lamp, a tungsten lamp, or the like)according to the average values of the R, G and B signals in each area.Ratios R/G and B/G between the average values of the R, G and B signalsin each area are calculated, and determination frames for the subjectlight sources are set on a co-ordinate system with the ratio R/G as thex coordinate and the ratio B/G as the y coordinate. The number of areasin each determination frame is determined, and the subject light sourcesis determined according to the brightness level of the subject and thenumber of areas in each determination frame (see Japanese PatentProvisional Publication No. 2000-224608). The method of determining thesubject light source (color temperature) is not limited to this.

After determining the subject light source, the CPU 138 determines thewhite balance correction values (gains) Rg, Gg and Bg that are suitablefor the subject light source and outputs them to the multipliers 130R,130G and 130B, respectively. The multipliers 130R, 130G and 130B outputsthe white-balanced R′, G′ and B′ signals to the gamma correcting circuit132.

The digital signal processing circuit 126 corrects the white balance inthe embodiment, but an analog signal processing including the CDScircuit 118 and a gain control amplifier (not shown) may do that. Theratios R/G and B/G are changed in the embodiment, but the chroma signalsCr and Cb may be changed.

The method of controlling the electronic flash 146 will now beexplained.

FIG. 14 is a block diagram of the electronic flash 146 that is built inor attached to the electronic camera 100. Parts that are the same asthose in FIG. 4 are denoted by the same reference numerals, and theywill not be explained.

The electronic flash 146 is different from the electronic flash 10 ofthe first embodiment in that it does not have the color temperaturesensors 24 for determining the color temperature of the subject lightsource. The color temperature is determined according to the R, G and Bsignals obtained from the CCD 114.

The CPU 138 outputs the light-emission signal in synchronization withthe shutter release and serial signals indicating the light emissionamount and the color temperature of the electronic flash light to thesystem controller 52 of the electronic flash 146.

A conventional electronic camera prohibits the light emission in themanual white balance mode, so that the electronic flash light does notaffect the manually-corrected white balance. However, the electroniccamera 100 of the present invention does not prohibit the light emissioneven in the manual white balance mode.

In addition, the conventional electronic camera does not perform eitherthe automatic white balance correction or the manual white balancecorrection, and adjusts the white balance with the fixed gains accordingto the electronic flash light (the daylight) to perform a shooting withthe electronic flash. However, the electronic camera 100 of the presentinvention performs the automatic white balance correction or the manualwhite balance correction.

The electronic camera 100 controls the electronic flash 146 to emit thelight with the automatically-measured color temperature of the subjectlight source in the automatic white balance mode. The electronic camera100 controls the electronic flash 146 to emit the light with themanually-set color temperature in the manual white balance mode.

Therefore, the electronic flash light does not affect the automaticallyor manually corrected white balance.

FIG. 15 is a perspective view of a light emitting head 190.

The light emitting head 190 has a rectangular diffusion plate 192, andR, G and B LEDs 193R, 193G and 193B are provided on the four sides ofthe diffusion plate 192, and a dish-shaped reflecting mirror 194 isarranged on the bottom of the diffusion plate 192. Mirrors may beprovided on parts of the sides of the diffusion plate 192 that are notin contact with the surface of LEDs 193R, 193G and 193B to prevent lightfrom leaking through the sides.

The LEDs 193R, 193G and 193B emit lights out of the diffusion plate 192through its top.

The number of the G LEDs 193G is larger than those of the R and B LEDs193R and 193B to produce a white light. A number of LEDs may be arrangedon the sides of the diffusion plate 192. The diffusion plate 192 doesnot necessarily have to be rectangular, and it may be a polygonal prismor a cylinder. A light guide member may be used instead of the diffusionplate 192, and a diffusion plate is provided only on its light emissionsurface.

According to the present invention, since the LEDs, the organic ELs orthe plasma light-emitting devices are used as the electronic flash lightsource, the light-emission (brightness) level and the light emissiontime can be easily changed. In addition, since the R, G and Blight-emitting devices are used, the color temperature of the electronicflash light can be manually or automatically changed. For example, backlight correction for the sun light in the morning or evening can beperformed according to the color temperature of the sun light, and thisprevents unnatural colors of a picture due to the electronic flashlight.

Moreover, since the large-capacity capacitor is charged slowly and itdischarges quickly, the electric energy can be obtained with the smallbattery. Furthermore, fall of the voltage of the battery can beprevented at the light emission, and misoperation of the other circuitscan be prevented.

The LEDs or the like can continuously emit the lights for slow shutterspeeds, and they can be used as a light source at the auto focus.

It should be understood, however, that there is no intention to limitthe invention to the specific forms disclosed, but on the contrary, theinvention is to cover all modifications, alternate constructions andequivalents falling within the spirit and scope of the invention asexpressed in the appended claims.

1. A method of emitting white light from a light emitting head,comprising the steps of: providing substantially transparent light guidemember having a top face, a bottom face, and at least one side face;providing at least one light emitting device in contact with said atleast one side face; providing a reflecting mirror in contact with thebottom face; providing reflecting mirrors in contact with surfaces ofsaid at least one side face which are not in contact with said at leastone light emitting device; and emitting light of a plurality ofdifferent colors from said at least one light emitting device into saidlight guide member; whereby white light is emitted through the top face.2. A light emitting apparatus comprising: a substantially transparentlight guide member; at least one light emitting element provided incontact with a face of said light guide member such that the lightemitted from said light emitting element is transmitted through the faceof said light guide member; and a light reflecting element provided onat least a side of said light guide member not provided with a lightemitting element; wherein the faces of said light guide member which areprovided with a light emitting element are further provided with a lightreflecting element disposed in contact with surfaces of the faces whichare not in contact with a light emitting element, and wherein lightemitted by said light emitting element propagates from said light guidemember through a light emission surface of said light guide memberopposite said light reflecting element.
 3. The light emitting apparatusof claim 2, wherein said light guide member comprises a substantiallysolid member.
 4. The light emitting apparatus of claim 3, wherein saidlight guide member is a diffusion plate.
 5. The light emitting apparatusof claim 3, further comprising a diffusion plate provided on the lightemission surface of said light guide member.
 6. The light emittingapparatus of claim 3, wherein said light guide member is a polygonalprism.
 7. The light emitting apparatus of claim 6, wherein said lightguide member is a rectangular prism.
 8. The light emitting apparatus ofclaim 3, wherein said light guide member is a cylinder.
 9. The lightemitting apparatus of claim 2, further comprising a plurality of lightemitting elements, wherein each of said light emitting elements isprovided in contact with a different face of said light guide member.10. The light emitting apparatus of claim 9, wherein said light emittingelements are comprised of LEDs.
 11. The light emitting apparatus ofclaim 10, wherein said LEDs comprise red, blue, and green LEDs.
 12. Thelight emitting apparatus of claim 11, wherein the number of green LEDsis greater than the number of red LEDs and also greater than the numberof blue LEDs.
 13. The light emitting apparatus of claim 12, wherein saidLEDs consist of a red LED, a blue LED, and first and second green LEDs.